Transformer winding with helically wound layers of a tape-like conductor

ABSTRACT

A transformer winding is formed of a tape-like conductor running helically in a plurality of layers in which the tape advances successively from one end of the layer to the other in overlapping relationship with the overlap increasing from layer to layer so that the length of the layers becomes progressively shorter towards the outside. Insulation between the successive helical coils is wound on at the same time that the layers are formed.

0 United States Patent 11 1 1111 3,928,832

Forsberg et a1. Dec. 23, 1975 1 TRANSFORMER WINDING WITH 2,328,443 8/1943 Foster 336/206 x ELCALLY WOUND LAYERS OF A 5323333 31322 i i 33278 1 ar TAPE-LIKE CONDUCTOR 3,691,498 9/1972 Zwelling et al. 336/223 X [75] Inventors: Svante Forsberg; Stig Larbo; Bjorn Stephens, a of Ludvika, Sweden FOREIGN PATENTS OR APPLICATIONS 6 W31 Asslgneel Allwanna Svenska Elekmska 3231332 13/133? $3,221.? 332330 Aktlebolaget, Vastems, Sweden 535,359 11/1955 Italy 336/206 333,785 3/1921 Germany 336/70 [22] Sept 1974 829,983 3/1960 United Kingdom 336/70 [21] Appl. No.: 511,304

Primary ExaminerThomas J. Kozma [30] Foreign Application Priority Data Sept. 28, 1973 Sweden 7313223 [57] ABSTRACT 52 us. c1. 336/70; 336/84; 336/206; A transform? wmdlng is of tape'like 336/233 ductor runmng helically m a plurallty of layers in [51] Int (12 HOIF 27/28 which the tape advances successively from one end of [58] Field 61 Search 336/69, 70, 84, 206, 223 layer medappmg relatonshp the overlap increasing from layer to layer so that the length of the layers becomes progressively shorter [56] UN lgferences Clted towards the outside. Insulation between the successive rTE STATES PATENTS helical coils is wound on at the same time that the lay- 1,011,791 12/1911 Hondd 336/206 erg are formed,

1,469,469 10/1923 Wright 336/206 1,932,640 10/1933 Rust 336/206 X 2 Claims, 5 Drawing Figures US. Patent Dec. 23, 1975 Sheet 1 of3 3,928,832

US. Patent Dec.23,1975 Sheet30f3 3,928,832

TRANSFORMER WINDING WITH HELICALLY WOUND LAYERS OF A TAPE-LIKE CONDUCTOR BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a transformer winding with a tape-like conductor and with turn insulation and layer insulation applied simultaneously with the conductor. It is primarily intended to be applied in the manufacture of windings for test transformers for very high voltage such as 600 kV but relatively moderate power, such as 600 kVA.

SUMMARY OF THE INVENTION According to the invention, such a winding is formed by simultaneously winding around a core a tape-like conductor in a series of layers each formed of a number of helical coils, the spacing of the coils being decreased from one layer to the next so that the length of the layers decreases outwardly. Insulation between the layers and'between successive turns of the helix is wound on at the same time as the tape.

The successive turns preferably overlap, with the amount of overlap increasing from one layer to the next. The insulation between the turns may be a separate strip wound on with the conductor or may be formed by parts of the layer insulation.

BRIEF DESCRIPTION OF THE DRAWINGS A In the drawings:

FIG. 1 shows a cross-section through a winding according to the invention;

FIG. 2 is a cross-section through two of the layers and illustrates the arrangement of separate turn and layer insulations;

FIG. 3 shows a form in which the layer insulation is also included in the turn insulation;

FIG. 4 shows in expanded view of the production of such a coil; and

FIG. 5 is a partial cross-section on the line 5-5 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a cross-section of an embodiment of the winding 13 arranged around a core leg which is interleaved with upper and lower yokes 11 and 12 of a transformer core. The winding is built up around a cylinder 1 of insulating material arranged around the core leg 10. The winding is built up as a layer winding with a tape-like conductor 3 and insulation between each turn and each layer. These insulations will be seen more in detail in FIGS. 2 and 3. The inner, low-voltage end of the winding is connected to the low-voltage terminal 2, as is seen at the left-hand bottom part of the winding. The high-voltage terminal 9 is connected to a plate 14 which is connected to the end of the outermost layer of the winding. The connection of terminal 9 to the plate 14 may be carried out in a way known per se, for example by welding or by screwing the terminal into a threaded socket on the plate.

The insulation between turns and layers thus consists of paper sheet and is wound up simultaneously with the tape-formed conductor 3. the turn insulation between successive turns of the conductor and layer insulation 5 winding. Conductor strip 3 and the turn insulation 4 run between the two sections 5a and 5b of layer insulation, so that as the unit is wound on the tape will overlie a previously wound section of 5a, and will be overlaid by a succeeding section of 5b.

Another alternativeis to use the same paper for both insulations. i

According to a third alternative, there are separate strips for the turn insulation, but completed with the paper sheets for the layer insulation, as shown in FIG. 3. The paper foil forming the turn insulation is wound up simultaneously with the conductor foil, but the paper sheet forming the layer insulation may be wound up intermittently by applying after a certain number of turns of the conductor and turn insulating foils (such as two or three) are wound up, a turn of layer insulating paper, of full width.

As appearsfrom FIG. 2 there is a metal screen 6 nearest the insulating cylinder 1. The layer insulation nearest the metal screen consists of several layers of full width paper, that is, the insulating paper 5a forming the layer insulation of somewhat wider than the axial length of the winding. As soon as winding of the conductor tape 3 starts, the width of the insulating paper in the layer insulation 5a under the winding layer decreases and the thickness of the layer insulation is successively increased, which results in an increase of the radial dimension of the winding layer as the layer of the winding tape 3 is laid upon the layer insulation 5a. The insulation between each turn of the winding consists of a separate tape 4 which is somewhat wider than the conductor tape 3 itself. The conductor tape 3 is placed directly upon the insulating tape 4 and both are wound up simultaneously as one unit.

When the insulating paper 5a forming the layer insulation under the conductor tape layer begins to decrease in width, a second insulating paper 5b is wound up on the conductor tape layer. The width of this second paper will increase by the same amount as the first insulating paper decreases, so that at each moment the sum of the width of the insulating papers above and below the conductor layer will be about the total axial length of the winding. This will be seen in FIG. 2.

At certain times during the winding of the layer insulation, control layers 7 are also applied at the ends of the winding for controlling the voltage along the sloping ends of the winding. The control layers work as capacitive voltage control elements along the ends of the winding, and they consist of metal foils. Each such layer is in the form of an open turn of the metal foil, that is, the two ends of the turn are separated by the insulating paper, as shown diagrammatically in FIG. 5.

The width of the foil is preferably some times greater than the width of the conductor foil. They are manufactured by laying a foil strip at proper points on the layer insulating paper during manufacturing of the layer insulation. The length of such a strip is about equal to the circumference of the winding at the point in question.

At the end of each layer of the conductor foil is inserted an edge screen 8 consisting of a separate turn of metal tape. This turn may be a turn of the winding but as an alternative it may be a separate turn, but then it may be electrically connected to the winding. The

3 outer edge of the edge screens 8 and the control layers 7 lie on a straight line, which will be seen in FIG. 1. The radial distance between two control layers is preferably the same as the distance between an edge screen and an adjacent control layer. The control layers 7 and the edge screens 8 form a voltage grading chain along the sloping ends of the winding.

FIG. 3 shows a form in which the layer insulation is manufactured from full width paper a throughout. Depending on the desire regarding the thickness of the layer insulation and considering the thickness of the paper, the number of turns of the tape conductor are determined for each turn of paper in the layer insulation. FIG. 3 shows that for every fourth layer of conductor and turn insulation a paper sheet is inserted in the layer insulation and that this paper is then included in the turn insulation as well.

From the foregoing it will be clear that the complete winding including the conducting foil layers, layer insulation, turn insulation, edge screens and voltage control layers are manufactured simultaneously beginning at the inner insulating cylinder 1 and going outwardly towards the plate 14.

By using a tape-formed conductor for thewinding and by manufacturing the turn insulation as well as the layer insulation simultaneously with the conductor winding, it is possible to maintain a constant number of turns in each layer. This is achieved by decreasing the pitch of the conductor and turn insulation tape from layer to layer, so that the conductor turns will overlap each other more and more as the winding operation continues. In this way the layer will be shorter and shorter in the axial direction and the complete winding is given the double-conical configuration as seen in FIG. 1. Thus a sufficient insulating distance to ground- 4 connected parts, such as yokes, is always maintained. Also the thickness of the layer insulation can be determined freely, independent of the number of conductor turns, turn insulation and the axial length of the winding.

Because there are in actuality a considerable number of layers, the decrease from layer to layer is relatively small, but it will be noted in FIG. 2 that the lower end of the second layer is slightly higher than that of the first layer.

The layerinsulation is built up of varnished paper. This paper, which can also be used for the turn insulation, is heated before being inserted into the winding, thus binding together all the materials included in the winding as the winding is being manufactured. The heating of the paper can be carried out by blowing hot air on the paper just before the paper enters the winding.

We claim:

1. A transformer winding comprising a tape-like conductor wound in a succession of over-lapping helical turns forming a plurality of layers with turn insulation between the turns and layer insulation between the layers, the overlap in successive layers increasing outwardly and the axial length of the layers decreases progressively.

2. In a winding as claimed in claim 1, the combination of open turns of metal tape enclosed in the layer insulation between the outer end portions of successive layers of the conductor, and edge screens of tape-like conductor material at the transition between successive layers, the radial distance between said turns and between a screen and an adjacent turn being substantially constant. 

1. A transformer winding comprising a tape-like conductor wound in a succession of over-lapping helical turns forming a plurality of layers with turn insulation between the turns and layer insulation between the layers, the overlap in successive layers increasing outwardly and the axial length of the layers decreases progressively.
 2. In a winding as claimed in claim 1, the combination of open turns of metal tape enclosed in the layer insulation between the outer end portions of successive layers of the conductor, and edge screens of tape-like conductor material at the transition between successive layers, the radial distance between said turns and between a screen and an adjacent turn being substantially constant. 